Nowadays, along with the advance of performance and diversity of downsized electronic equipment such as cellular phones and the like, panel switch having a plurality of arranged push switches and mainly used in operation section of them is required to have high accuracy and usability as well as cheap prices.
A conventional movable contact unit for push switches used in operation section of downsized electronic equipment and a panel switch using the movable contact units are described with reference to FIG. 10 through FIG. 13. Here, perpendicular scale in each drawing is drawn enlarged for easy understanding.
FIG. 10 shows a cross-sectional front view of a conventional movable contact unit, FIG. 11 shows an exploded perspective view of the conventional movable contact unit. In FIG. 11, movable contact 1 formed from a resilient thin metal sheet has a dome shape and base sheet 2 formed from a flexible insulation substrate has a plurality of through holes 2A in predetermined positions. Movable contact 1 is placed in each through hole 2A of base sheet 2. Cover sheet 3 formed from a flexible insulation substrate and coated with adhesive material 3A on bottom surface is bonded on individual convex upper surface of movable contact 1 and is fixed on base sheet 2 to form a movable contact unit 4 having a plurality of push switches.
FIG. 12 shows a cross-sectional front view of a panel switch using an above mentioned conventional movable contact unit, and FIG. 13 shows an exploded perspective view of the panel switch. In FIG. 13, stationary contact substrate 5 has a plurality of stationary contact 7 consisted of central stationary contact 7A and peripheral stationary contact 7B on predetermined positions of hard plate-like insulation board 6. Peripheral edge of each movable contact 1 of movable contact unit 4 is placed on corresponding peripheral stationary contact 7B such that convex bottom surface of movable contact 1 faces each central stationary contact 7A, basing on small hole 5A of substrate 5 and small hole 2B of base sheet 2 for positioning, to form panel switch 8 having a plurality of arranged push switches.
Panel switch 8 mentioned above is mounted on an operation section of electronic equipment. When convex upper surface of a movable contact 1 is depressed by operation button (not shown) through cover sheet 3, convex bottom surface of movable contact 1 performs resilient motion with a click feeling to connect central stationary contact. Then, central stationary contact 7A of stationary contact substrate 5 and outside stationary contact 7B are electrically coupled to make a push switch ON stage. Upon release of depression from operation button, a resilient restoring force of movable contact 1 acts to disconnect convex bottom surface from central stationary contact 7A to return to push switch OFF stage as shown in FIG. 12.
However, in above mentioned conventional movable contact unit 4 and panel switch using the movable contact unit, ingress of dust between movable contact unit 4 and stationary contact substrate 5 moves in between movable contact 1 and stationary contact 7 to cause problems of loose connection in push switch of panel switch, during use of electronic equipment incorporated with panel switch having a combination of movable contact unit 4 and stationary contact substrate 5.